Strong Absorptive Regge-Cut Model for Pion Photoproduction,np→pn, and Related Processes

The combined high-energy data for $\gamma p\to {\pi }^{+}n$, $\gamma n\to {\pi }^{-}p$, $\mathrm{np}\to \mathrm{pn}$, $\overline{p}p\to \overline{n}n$, $\gamma p\to {\pi }^{0}p$, and $\gamma p\to \eta p$ are successfully described in a strong absorptive (Regge-cut) model. Only the high-lying trajectories, $\omega$, $\rho$, $A_2$, and (evasive) $\pi$ and the associated cuts are necessary to understand the data. The ${\pi }^{\pm }$ photoproduction cross-section difference rules out "non-sense wrong-signature zeros." The scale of the cross sections is determined correctly by the conventional coupling strengths. The general features of pion exchange are discussed.